Power converter

ABSTRACT

A low noise, compact and low cost electric power converter employing a compact common mode transformer, and incorporating a line filter can reduce a leakage current, and can maintain predetermined leakage current reduction effect even if installation condition of the electric power converter or a characteristics of a semiconductor switching element is varied. The electric power converter including a capacitor, a first electrode, a second electrode, a first magnetic body, on which the first electrode and the second electrode are wound to form an LC composite element, connecting electrodes electrically connected to respective of both ends of the first and second electrodes, a second magnetic body for interlinking both ends of the first magnetic body, a coil wound around the second magnetic body in the same winding direction as the first and second electrodes wound around the first magnetic body and a resistor for shorting the output of the coil.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to an electric powerconverter, such as an inverter unit, a power storage unit and so forth.More particularly, the invention relates to an electric power converterusing an LC composite element reducing noise leaking from the electricpower converter.

[0003] 2. Description of the Related Art

[0004] An inverter unit has been widely used for operation of analternating-current motor, such as an induction motor or the like. Inthe recent years, the inverter unit is also used as a controller for apower source of a vehicle so that a merit of variable speed operation bythe inverter unit can be enjoyed satisfactorily.

[0005] In control of the conventional inverter unit shown in FIG. 16,PWM (pulse-width modulation) control systems have been widely usedconventionally. The PWM control system includes a converter portion(forward converting portion) 2 constituted of a diode rectifier, a PWMcontrol type inverter (reverse converting portion) 3, to which a directcurrent power output from the converter portion 2 is input, and asmoothing capacitor 4 connected in a direct current portion between theconverter portion 2 and the inverter portion 3.

[0006] When an alternating-current power is input to the converterportion 2 from a commercial alternating-current source to be the powersource, a direct-current power smoothed by the capacitor 4 is suppliedto the inverter portion 3. Here, a semiconductor switching element 40 ofthe inverter portion 3 is PWM controlled to be converted into apredetermined voltage of the direct current power and an alternatingcurrent power of a predetermined frequency. As a result, a power ofvariable voltage and variable frequency is supplied to a load 6, such asinduction motor or the like.

[0007] At this time, the semiconductor switching element 40 in theinverter portion 3 is controlled ON (conductive) and OFF(non-conductive)according to a PWM signal transmitted from a computer 28 via a drivercircuit 43, and outputs a rectangular wave voltage and a load current tothe load 6 to cause conduction loss determined by a conductionresistance of the semiconductor switching element 40 and the loadcurrent and a switching loss upon occurrence of transitional abnormalityof voltage and current upon ON and OFF.

[0008] In the recent years, improvement of transient response of thesemiconductor switching element 40 has been progressed in order toreduce the switching loss and IGBT (insulated gate bipolar transistor)having high speed switching characteristics has been developed torealize reduction of loss to contribute for down-sizing of the cooler ofthe device and down-sizing of the electric power converter representedby the inverter.

[0009] However, when transient voltage variation of the rectangular wavebecomes acute, a current leaking from an earth capacitance 7 of thepower cable connecting between an alternating-current motor asrepresentative load 6 and an earth capacitance 7 of a winding of thealternating-current motor (hereinafter referred to as “leakage current”)is increased to elevate a peak value of the leakage current 8 inproportion to a rate of variation of the voltage relative to a time tocause high frequency resonation with parasitic inductance 50 of a powerline. Also, the leakage current 8 may flows into the commercialalternating-current source 1 through the inverter portion 3 or theinverter 2 to affect to other equipments, such as to cause malfunction.Furthermore, the leakage current and an electromagnetic wave generatedby wiring voltage of a leakage current path may penetrate into otherequipments or to discharge radiation noise to television and/or radioantennas adjacent to the inverter.

[0010] As one example of prior art, the electric power converteremploying the converter (forward converting portion) 2 constituted ofthe diode rectifier has been discussed hereabove. However, even with theelectric power converter supplied a direct-current power output from astorage cell, such as a battery or the like, power of variable voltageand variable frequency can be supplied to the load 6, such as a powersource of a vehicle, a cooling fan of a cooling device, a pump drivingmotor for circulating a cooling water, a hydraulic pump driving motorfor hydraulic machine, a compressor driving motor for air conditionerand so forth by converting the direct-current power into thealternating-current power with a predetermined voltage and apredetermined frequency by PWM controlling the semiconductor switchingelement 40 of the inverter portion 3. Even in this case, radiation noiseis generated.

[0011] Here, in order to preventing the leakage current 8 to be a causeof noise from flowing, a line filter 5 constituted of an X-connectioncapacitor 52 and a Y-connection capacitor 10 connecting a common modetransformer 9 as passive element connected to the power line shown inFIG. 16, the power line and the ground, is inserted in the input powerline of the electric power converter in series with the load 6 or thepower source for blocking flow of the high frequency leakage current 8to the common mode transformation 9. Then, the blocked leakage current 8flows to the Y-connection capacitor 10 and then fed back to the groundto significantly reduce the leakage current 8 flowing into the inputpower line, to avoid for other equipment to cause malfunction or thelike, to reduce the leakage current 8 and electromagnetic wave generatedby wiring voltage of the leakage current path so as not to penetrateinto other equipment.

[0012] For down-sizing the line filter, there has been proposed the linefilter 5 employing an LC composite element 15 disclosed in JapanesePatent Application Laid-Open No. 6-224045. As shown in FIG. 17, an anode16 and a cathode of the capacitor are wound around a bar shaped magneticbody 19 of ferrite or the like in concentric manner to form the LCcomposite element 15 with the anode 16 and the cathode 17. The formed LCcomposite element 15 serves as the common mode transformer in the mannerof winding. In order to form the X-connection capacitor 52 and theY-connection capacitor 10 between the anode 16 and cathode 17, and theground, third and fourth electrodes are wound together with the anode 16and the cathode 17 to form the line filter 5 to realize compact and highperformance line filter 5 for significantly reducing the leakage current8 flowing in the input power line, for avoiding adverse effect, such asmalfunction in other equipment, for reducing electromagnetic wave to begenerated by the leakage current 8 and the wiring voltage of the leakagecurrent path to avoid penetration into other equipment.

[0013] On the other hand, a method for damping the leakage current 8 byinserting a resistor 13 in the path to flow the leakage current 8, hasbeen developed and reported in Institute of Electrical Engineers, 1995Industrial Application Department National Convention No. 93 “HighFrequency Leakage Current Restriction Effect and Designing Method usingCommon Mode Transformer”. In the method, the same phase winding to bezero-phase coil 26 is newly added to the common mode transformer 9 isinserted in the power line in series (hereinafter, the common modetransformer added the same phase winding will be referred to as CMT) forlinking magnetic flux generated in a core portion of the common modetransformer 9 by the leakage current flowing through the power line tothe newly added zero-phase coil 26 to short the output of the zero-phasecoil 26 by a resistor 13. Thus, common mode current, namely the leakagecurrent 8 flows through the resistor 13 for damping the leakage current8 to significantly reduce the leakage current flowing through the powerline to prevent adverse effect for other equipment, such as causingmalfunction, to reduce the leakage current and electromagnetic wavegenerated by the wiring voltage of the leakage current path to avoidpenetration into other equipment.

[0014] Conventionally, flow of the leakage current 8 to be a cause ofnoise is restricted using the line filter 5 constructed with the commonmode transformer 9 connected to the power line, and the capacitors 10,52 connected between the power line and the ground. In such case, thecommon mode transformer 9 to be used for the line filter 5 has to beprovided a relatively large inductance characteristics in the extent ofseveral mH. It is further required to accurately wind electricalconductor for a several turns on a magnetic core per each phase and anelectrical conductor having relatively large diameter flowing the loadcurrent to the wound conductor. Therefore, size of the common modetransformer 9 becomes large and size of the line filter 5 becomes large.In case of the electric power converter having output of several kW, theline filter 5 becomes a size comparable with the electric powerconverter in such a manner that the line filter 5 has to be constructedin a casing separated from a casing of the electric power converter toencounter the problem of make the electric power converter bulky andhigh cost of the line filter 5.

[0015] Furthermore, in case of the line filter employing theconventional LC composite element 15, it is necessary to make theinductance value for shielding the leakage current 8 large for operationas passive circuit. To attain large inductance value, number of turns inwinding the electrodes forming the common mode transformer 9 or, in thealternative, thickness of the magnetic body to be a core, such asferrite is increased. In the former case, thickness is further increasedfor increased length of insulation paper. In either case, difficulty isencountered in down-sizing the line filter.

[0016] On the other hand, a circuit constants of the line filter 5 andCMT 11 are determined to achieve some reduction effect for the leakagecurrent 8 within a range where installation condition of the electricpower converter is determined by safety standard and so forth.Naturally, when one of installation conditions, such as a length of thepower cable connecting the electric power converter and the load,characteristics of leakage capacity, is varied, it is possible that thedesired reduction characteristics of leakage current 8 cannot beobtained. For instance, when the power cable is provided greater lengththan the predetermined value, it is possible that the desired reductioncharacteristics of leakage current 8 cannot be obtained. Particularly,in the line filter 5, when the characteristics of the semiconductorswitching element 40 to be used in the electric power converter isvaried or when the driver circuit 43 of the semiconductor switchingelement 40 is varied, a transient output voltage characteristics of thesemiconductor switching element 40 becomes different to vary thewaveform of the leakage current 8. Also, due to difference of frequencycomponent to be contained in the leakage current, predetermined noisereduction characteristics cannot be obtained by the line filter 5.

[0017] Furthermore, in the technology disclosed in Japanese PatentApplication Laid-open No. 2000-60407, the common mode current, namelythe leakage current 8 can be damped by flowing the leakage currentthrough the resistor 13 by inserting the CMT reported in Institute ofElectrical Engineers, 1995 Industrial Application Department NationalConvention No. 93 “High Frequency Leakage Current Restriction Effect andDesigning Method using Common Mode Transformer” between the converterportion as a power input stage of the electric power converter and theinverter portion to be an output stage for supplying the power to theload in parallel to the smoothing capacitor, and whereby can reduce theleakage current flowing through the power line significantly to reduceadverse effect for other equipment possibly cause malfunction. Also, theleakage current 8 and the electromagnetic wave to generate by the wiringvoltage of the leakage current path can be reduced to avoid the problemof penetration into other equipment.

SUMMARY OF THE INVENTION

[0018] The present invention has been worked out in view of thedrawbacks set forth above. Therefore, it is an object of the presentinvention to provide a low noise, compact and low cost electric powerconverter employing a compact common mode transformer, and incorporatinga line filter which can reduce a leakage current, and can maintainpredetermined leakage current reduction effect even if installationcondition of the electric power transformer or a characteristics of asemiconductor switching element is varied.

[0019] According to the first aspect of the present invention, anelectric power converter including a capacitor disposed in a powerwiring for supplying an electric power to a load, comprises:

[0020] a foil form first electrode fixed on a first insulation sheet;

[0021] a foil form second electrode fixed on a second insulation sheet;

[0022] a bar-shaped first magnetic body, on which the first electrodewith the first insulation sheet and the second electrode with the secondinsulation sheet are wound in overlapping manner to form an LC compositeelement;

[0023] connecting electrodes electrically connected to respective ofboth ends of the first and second electrodes;

[0024] a second magnetic body having both ends located in contact withor close proximity with both ends of the first magnetic body forinterlinking both ends of the first magnetic body;

[0025] a coil wound around the second magnetic body in the same windingdirection as the first and second electrodes wound around the firstmagnetic body; and

[0026] a resistor for shorting the output of the coil.

[0027] In the preferred construction, the electric power converter mayfurther comprise:

[0028] a both end opened cylindrical casing, in which the LC compositeelement is disposed;

[0029] seal plates formed of insulation material, fixed on both ends ofthe cylindrical casing for closing the both end opening, and definingthrough openings, through which the connecting electrode and firstmagnetic body extend;

[0030] the second magnetic body being arranged on outside of thecylindrical casing linking both ends of the first magnetic body andbeing fixed side surface of the cylindrical casing and the seal plate bya jig or adhesive.

[0031] A jig for fixing the second magnetic body and fixing the LCcomposite element on a wiring board, may be secured on the cylindricalcasing or the seal plate.

[0032] According to the second aspect of the present invention, anelectric power converter including a capacitor disposed in a powerwiring for supplying an electric power to a load, comprises:

[0033] a foil form first electrode fixed on a first insulation sheet;

[0034] a foil form second electrode fixed on a second insulation sheet;

[0035] a bar-shaped first magnetic body, on which the first electrodewith the first insulation sheet and the second electrode with the secondinsulation sheet are wound in overlapping manner with placing the firstelectrode on upper layer to form a first LC composite element;

[0036] a bar-shaped third magnetic body, on which the first electrodewith the first insulation sheet and the second electrode with the secondinsulation sheet are wound in overlapping manner in the same windingdirection as the first electrode with the first insulation sheet and thesecond electrode with the second insulation sheet of the first LCcomposite element, with placing the second electrode on upper layer toform a second LC composite element, the second electrode of the secondLC composite element being electrically connected to the secondelectrode of the first LC composite element for establishing seriesconnection of the first LC composite element and the second LC compositeelement;

[0037] fourth and fifth magnetic bodies having both ends located incontact with or close proximity with both ends of the first and thirdmagnetic bodies for interlinking both ends of the first and thirdmagnetic bodies;

[0038] a coil wound around one of the fourth and fifth magnetic bodiesin the same winding direction as the first and second electrodes woundaround the first magnetic body; and

[0039] a resistor for shorting the output of the coil.

[0040] Preferably, the electric power converter may further comprise:

[0041] connecting electrodes electrically connected to respective ofboth ends of the first and second electrodes of the first and second LCcomposite elements;

[0042] both end opened cylindrical casings, in which the first andsecond LC composite elements are disposed;

[0043] seal plates formed of insulation material, fixed on both ends ofthe cylindrical casings for closing the both end opening, and definingthrough openings, through which the connecting electrodes and first andthird magnetic bodies extend;

[0044] the second magnetic body being arranged on outside of thecylindrical casing linking both ends of the first magnetic body andbeing fixed side surface of the cylindrical casing and the seal plate bya jig or adhesive.

[0045] The output of the coil may be shorted by a variable resistor, and

[0046] the electric power converter may further comprise means forvarying resistance value of the variable resistor for a plurality oftimes, and measuring voltage at both ends of the variable resistor atevery occasion of varying the resistance value, and

[0047] calculating means for deriving the resistance value of thevariable register for minimizing a common mode current flowing throughthe LC composite element using the detected voltage at the variableresistor. An inverter unit using a pulse width modulation system forconverting a direct-current power into an alternating-current power maybe secured on a side surface of an electric motor as the load, forintegrating the inverter unit with the load, the LC composite elementmay be used for smoothing the direct-current power of an inverterportion.

[0048] An electric power converter mounted on a vehicle and having aninverter unit for driving a motor as a load using a pulse widthmodulation system for converting a direct-current power into analternating-current power may include an LC composite element used forsmoothing the direct-current power of an inverter portion.

[0049] An electric power converter having an inverter unit supplying anelectric power to a power source system with converting a direct-currentpower supplied from a solar cell or a power storage cell using a pulsewidth modulation system may include an LC composite element used forsmoothing the direct-current power of an inverter portion.

[0050] In the preferred construction, the first electrode with the firstinsulation sheet and the second electrode with the second insulationsheet of the LC composite element for smoothing the direct-current powerof the inverter unit may be wound to have compressed planular shape incross section on a plane perpendicular to a winding axis, and thebar-shaped first magnetic body may be inserted in the center portion ofthe electrode wound into the compressed planular shape. Also, it ispossible that regions having mutually different surface roughness may beformed on surfaces of respective anode and cathode of the LC compositeelement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will be understood more fully from thedetailed description given hereinafter and from the accompanyingdrawings of the preferred embodiment of the present invention, which,however, should not be taken to be limitative to the invention, but arefor explanation and understanding only.

[0052] In the drawings:

[0053]FIG. 1 is a section showing the first embodiment of an LCcomposite element according to the present invention;

[0054]FIG. 2 is a side elevation of the first embodiment of the LCcomposite element of FIG. 1;

[0055]FIG. 3 is a circuit diagram of an electric power converteremploying the first embodiment of the LC composite element of FIG. 1;

[0056]FIG. 4 is a development elevation of an internal electrodes of thefirst embodiment of the LC composite element of FIG. 1;

[0057]FIG. 5 is a perspective view showing a construction showing theinternal electrode of the first embodiment of the LC composite elementof FIG. 1;

[0058]FIG. 6 is a schematic equivalent circuit of a leakage current pathof the electric power converter employing the first embodiment of the LCcomposite element of FIG. 1;

[0059]FIG. 7 is a circuit diagram showing the second embodiment of theLC composite element according to the present invention and the electricpower converter employing the second embodiment of the LC compositeelement;

[0060]FIG. 8 is a flowchart showing a minimizing process of the leakagecurrent in the electric power converter of the embodiment shown in FIG.7;

[0061]FIG. 9 is a section of the third embodiment of the LC compositeelement according to the present invention;

[0062]FIG. 10 is a side elevation showing the third embodiment of the LCcomposite element of FIG. 9;

[0063]FIG. 11 is a circuit diagram showing a main circuit of theelectric power converter employing the third embodiment of the LCcomposite element shown in FIG. 9;

[0064]FIG. 12 is a circuit diagram showing a main circuit of theelectric power converter employing the fourth embodiment of the LCcomposite element according to the present invention;

[0065]FIG. 13 is a fragmentary illustration showing the electric powerconverter employing the fifth embodiment of the LC composite elementaccording to the present invention;

[0066]FIG. 14 is a schematic circuit diagram showing the electric powerconverter employing the LC composite element according to the presentinvention;

[0067]FIG. 15 is a schematic circuit diagram showing the electric powerconverter employing the LC composite element according to the presentinvention;

[0068]FIG. 16 is a circuit diagram of the electric power converteremploying the conventional line filter and CMT;

[0069]FIGS. 17A and 17B show constructions of the conventional LCcomposite circuit and equivalent circuit;

[0070]FIG. 18 is a section showing the embodiment of the electric powerconverter employing the sixth embodiment of the LC composite elementaccording to the present invention; and

[0071]FIG. 19 is an illustration showing the embodiment of the electricpower converter employing the seventh embodiment of the LC compositeelement according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0072] The present invention will be discussed hereinafter in detail interms of the preferred embodiment of the present invention withreference to the accompanying drawings. In the following description,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be obvious, however, tothose skilled in the art that the present invention may be practicedwithout these specific details. In other instance, well-known structureis not shown in detail in order to avoid unnecessary obscurity of thepresent invention.

[0073]FIG. 1 is a section showing the first embodiment of an LCcomposite element according to the present invention, FIG. 2 is a sideelevation of the first embodiment of the LC composite element of FIG. 1,and FIG. 3 is a circuit diagram of an electric power converter employingthe first embodiment of the LC composite element of FIG. 1. A generalconstruction of the electric power converter has a main circuitincluding a converter portion 2 constituted of a diode rectifierrectifying a commercial alternating-current power source 1 shown in FIG.16, a PWM control type inverter portion 3 receiving an input of adirect-current power output from the converter portion 2 and a smoothingcapacitor 4 connected to a direct-current portion between the converterportion 2 and the inverter portion 3.

[0074] A line filter 5 of the electric power converter used for generalpurpose is connected to the converter portion 2 on the side of acommercial alternating-current power source 1. A leakage current 8flowing out from a leakage capacity 7 between an alternating-currentmotor as a load 6 or a power line of the alternating-current motor andthe ground, is blocked from flowing through by rising a high frequencyline impedance with a choke coil having superior high frequencycharacteristics so that the leakage current 8 may not be transmittedtoward the commercial alternating-current power source 1. The leakagecurrent 8 is grounded through a Y-connection capacitor 10 connected tothe ground in one side and connected to a power line on the other sideand having superior frequency response and whereby is prevented fromflowing out to the commercial alternating-current power source 1.

[0075] On the other hand, the conventional CMT 11 is disposed in thepower line between the inverter portion 3 which is PWM controlled sothat a sum of output currents IU, IV, IW of a three phase inverterbecomes zero, and a load 6, in series. The CMT 11 is formed by windingthree power wiring in the same phase and a zero-phase coil 26 on atoroidal core. The output of the zero-phase coil 26 is shorted by aresistor 13. Then, load currents flowing through respective phases formmagnetic fluxes which are combined in a magnetic circuit in the toroidalcore. However, a sum of the magnetic fluxes generated by IU, IV and IWnaturally becomes zero. Therefore, residual magnetic flux in themagnetic circuit is only component generated by the leakage current 8.Thus, a magnetic flux is induced in the zero-phase coil 26 by theleakage current 8. Thus, the leakage current 8 flows through theresistor 13 shorting the output of the zero-phase coil 26. This isequivalent to that the resistor 13 is inserted in the path to flow theleakage current 8 in series. Thus, effect to damp the leakage current 8by the resistor 13 can be achieved.

[0076] The first embodiment shown in FIGS. 1, 2 and 3 are differentiatedfrom the prior art shown in FIGS. 16 and 17 in the following points. Inthe electric power converter employing the inverter portion 3, theconverter portion 3 and an LC composite element 15 used as a smoothingcapacitor 4 in the power wiring connecting the inverter portion 3, theconverter portion 2 and a power storage portion 14, an anode 16 and acathode 17 are fixed on an insulation paper 18 having dielectricconstant at least greater than that of air or an insulation paper 18wetted by an electrolytic solution, as shown in FIG. 4. The anode 16 andcathode 17 are wound around a bar shaped magnetic body, such as ferriteor the like having length at least greater than a width of theinsulation paper 18 in overlapping manner to form a capacitor as shownin FIG. 5. Connection electrodes 20 are fixed on both ends of the anode16 and the cathode 17 for external electrical connection. The capacitorthus constructed is disposed within a cylindrical casing 21 havingopened both ends in a manner shown in FIG. 1. Seal plates 22 formed ofresin or the like are fixed at both ends of the cylindrical casing 21.Through holes through which the connection electrode 20 and thebar-shaped magnetic body 19 are extended out of the cylindrical casing21, are formed in the seal plates 22. In the outside of the cylindricalcasing 21, a channel-shaped magnetic body 23 is provided with placingboth ends close proximity with both ends of the bar-shaped magnetic body19 to form a toroidal magnetic circuit. The channel-shaped magnetic body23 is secured on the side surface of the cylindrical casing 21 by meansof a jig or a support member 24. On the channel-shaped magnetic body 23,a coil bobbin 25 is mounted. A third coil to be the zero-phase coil 26is wound around the coil bobbin 25. The coil bobbin 25 is fixed at apart of the LC composite element 15. An output of the zero-phase coil 26is shorted by the resistor 13 having a predetermined resistance. Thus,as shown in FIG. 3, the resistor 13 can be inserted in the common modeleakage current 8 flowing across the inverter portion 3, the converterportion 2 and the power storage portion 14 to flow the leakage current 8through the resistor and whereby to damp the leakage current 8. With thearrangement set forth above, the leakage current 8 flowing through thepower line can be reduced to eliminate adverse effect to other equipmentwhich can cause malfunction. Also, electromagnetic wave generated by theleakage current 8 and the wiring voltage of the leakage current path canbe reduced. Therefore, the leakage current 8 can be damped without newlyusing the line filter 5 with built-in common mode transformer 9 toachieve lowering of noise, down-sizing and lowering of cost of theelectric power converter.

[0077]FIG. 7 shows one example of the electric power converter employingthe second embodiment of the LC composite element according to thepresent invention. The shown embodiment is differentiated from theembodiment shown in FIG. 1 in the following points. On thechannel-shaped magnetic body 23, the coil bobbin 25 is mounted. Thethird coil to be the zero-phase coil 26 is wound around the coil bobbin25. The coil bobbin 25 is fixed at a part of the LC composite element15. An output of the zero-phase coil 26 is shorted by a variableresistor 27 having a predetermined resistance. Thus, as shown in FIG. 3,the variable resistor 27 can be inserted in the common mode leakagecurrent 8 flowing across the inverter portion 3, the converter portion 2and the power storage portion 14. Resistance value of the variableresistor 27 is varied for a plurality of times using a computer 28according to a process illustrated in a flowchart shown in FIG. 8, ateach time of varying the resistance value (Rz(N)), a voltage (Vr(N)) atboth ends of the variable resistor 27 is measured. In measurement, thevoltage at both ends of the resistor is rectified by a half-waverectifier circuit 29 and held by a peak hold circuit 30 or a sample/holdcircuit. The held value is then converted into the digital value fromthe voltage by an A/D converter 31. On the basis of the converteddigital value, the resistance value (Rz) of the variable resistor 27, atwhich the common mode leakage current 8 becomes minimum, is calculatedby the computer 28. On the basis of the result of calculation, theresistance value (Rz) of the variable resistor 27 is set to thedetermined resistance value by controlling the resistance controller 32from the computer 28. The leakage current 8 can be damped using theresistor 27 which can minimize the leakage current. By this,irrespective of mounting condition of the electric power converter andthe load 6, the leakage current flowing through the power line can bereduced significantly to reduce the leakage current 8 flowing into otherequipment via the commercial alternating-current power source 1 and toreduce adverse effect for other equipment to possibly cause malfunction.Also, electromagnetic wave generated by the leakage current 8 and thewiring voltage of the leakage current path can be reduced. Therefore,the leakage current 8 can be damped without newly using the line filter5 with built-in common mode transformer to achieve lowering of noise,down-sizing and lowering of cost of the electric power converter.

[0078]FIG. 9 shows one example of a section of the third embodiment ofthe LC composite element according to the present invention, FIG. 10 isa side elevation of the LC composite element shown in FIG. 9 and FIG. 11shows one example of the construction of the electric power converteremploying the shown embodiment of the LC composite element. The shownembodiment is differentiated from the embodiment shown in FIGS. 1 and 7in the following points. As shown in FIG. 11, a first LC compositeelement 33 and a second LC composite element 34 respectively serving assmoothing capacitor are disposed in the power wiring connecting theinverter 3, the converter 2 and the power storage portion 14. The firstLC composite element 33 is located on positive side of thedirect-current power and the second LC composite element 34 is locatedon negative side of the direct-current power. Similar to FIG. 5, ananode 35 and a cathode 36 of the first LC composite element 33 aresecured on an insulation paper 18 or an insulation paper 18 wetting byelectrolytic solution having a dielectric constant at least greater thanair. The anode 35 and the cathode 36 are wound on the bar-shapedmagnetic body 19, such as ferrite or the like having axial length atleast greater than the width of the insulation paper 18 with placing theanode 35 on upper side to form a capacitor. The connecting electrodes 20are fixed for external connection of both ends of the anode 35 and thecathode 36. The capacitor is disposed in the both end opened cylindricalcasing 21. Then, seal plates 22 formed of a resin or the like are fixedon both ends of the cylindrical casing 21. Through holes are formed inthe seal plate so that the connection electrode 20 and the bar-shapedmagnetic body 19 may extend outside of the cylindrical casing. An anode37 and a cathode 38 of the second LC composite elements 34 are wound onthe bar-shaped magnetic body 19 with placing the cathode 38 upper sideopposite to the anode 35 and the cathode 36 of the first LC compositeelement 33. Respective bar-shaped magnetic bodies 19 of the first andsecond LC component elements are connected by two connecting magneticbodies 39 provided outside of the cylindrical casing 21 to form toroidalmagnetic circuit. By connecting the cathode 36 of the first LC compositeelement 33 and the anode 37 of the second LC composite element 34, thefirst and second LC composite elements 33 and 34 are connected inseries. The coil bobbin 25 is mounted one of the connecting magneticbodies 29 located outside of the cylindrical casing 21. On the coilbobbin 25, the third coil serving as the zero-phase coil 26 is wound.The coil bobbin 25 is secured at a portion of the LC composite element15 for shorting the output of the zero-phase coil 26 to the resistor 13having predetermined resistance. With the construction set forth above,the resistor 13 can be inserted in the path of the common mode leakagecurrent flowing across the inverter 3, the converter 2 and the powerstorage portion 14 for damping the leakage current 8. Furthermore, uponseries connection of the LC composite element 15, the second LCcomposite element 34 having order of winding of the anode 37 and thecathode 38 opposite to that of the anode 35 and the cathode 36 of thefirst LC composite element 33. Thus, the position of the anode 35 of thefirst LC composite element 33 to be a positive side potential of thedirect-current power and the cathode of the second LC composite element34 to be a negative side potential of the direct-current power arelocated at symmetrical position relative to the bar-shaped magnetic body19 to permit lowering of error magnetic flux due to offset of theelectrode positions. Thus, high precision common mode transformer can beformed. b Also, it can prevent heating or breakage of the resistor 13 bythe erroneously detected common mode current (leakage current) to permitonly leakage current 8 from the leakage capacitance 7 of the electricpower converter and the load 6 to flow through the zero-phase coil 26 tosignificantly reduce the leakage current 8 flowing into the power lineand to reduce leakage current 8 flowing into other equipment via thecommercial alternating-current power source 1 to reduce adverse effectfor other equipment possibly cause malfunction. Therefore, the leakagecurrent 8 can be damped without newly using the line filter 5 withbuilt-in common mode transformer to achieve lowering of noise,down-sizing and lowering of cost of the electric power converter.

[0079]FIG. 12 shows one embodiment of the electric power converteremploying the fourth embodiment of the LC composite element according tothe present invention. The shown embodiment is differentiated from theembodiment shown in FIGS. 1 and 7 in the following points. On theelectrode of inverter portion 3 side of the anode 16 and the cathode 17of the LC composite element 15 connected to the direct-current powerline or on the side of the converter portion 2 and the power storageportion 14, a typical smoothing capacitor 4 is connected in parallel tothe LC composite element 15. The output of the third coil serving as thezero-phase coil 26 is shorted by the resistor 13 or the variableresistor 27. By inserting the resistor 13 or the variable resistor 27and by setting the resistance value so that the leakage current 8becomes minimum, damping of the leakage current becomes possible. Byconnecting the smoothing capacitor 5 in parallel to the LC compositeelement 15, the leakage current 8 flowing through the power line can bereduced significantly with easily increasing capacity of the smoothingcapacitor to reduce the leakage current 8 flowing into other equipmentvia the commercial alternating-current power source 1. Also,electromagnetic wave generated by the leakage current 8 and the wiringvoltage of the leakage current path can be reduced. Therefore, theleakage current 8 can be damped without newly using the line filter 5with built-in common mode transformer 9 to achieve lowering of noise,down-sizing and lowering of cost of the electric power converter.

[0080]FIG. 13 shows one embodiment of the electric power converteremploying the fifth embodiment of the LC composite element according tothe present invention. The shown embodiment is differentiated from theformer embodiment. As shown in FIG. 13, a power module 41 incorporatinga semiconductor switching element 40 for the inverter portion 3 and theconverter portion 2 is housed within an outer casing 12 of the electricpower converter formed of aluminum die-cast as shown in FIG. 13. Acooler 42 of the power module 41 is fixed to the outer casing 12 bymeans of threaded fasteners and so forth. In the upper portion of thepower module 41, the LC composite element 15, a terminal base 53, adriver circuit 43 controlling a power semiconductor, the computer 28performing PWM control, a communication circuit 45 transferring thesignal from the superior controller of the electric power converter tothe computer 28, and a control board 47, on which a power source circuit46 is mounted, are arranged to form the electric power converter byconnecting with the electrode of the power module 41 by solder or thelike. The outer casing 12 and an outer casing of the alternating-currentmotor as the load 6 are integrated. Upon integration, the outer casing12 and the outer casing 44 may be combined and fixed by screws or bolts.When the alternating-current motor as the load 6 and the electric powerconverter are located in close proximity with each other, length of anoutput power wiring connecting the inverter portion 3 generating theleakage current 8 and the load 6 can be maintained constant under allmounting conditions. As a result, variation of the leakage current 8depending upon mounting condition can be eliminated. Therefore, theshorting resistor 13 of the zero-phase coil 26 for minimizing theleakage current 8 can be determined univocally on the basis of theleakage capacitance of the alternating-current motor to accuratelyrealize damping effect of the leakage current 8. With the arrangementset forth above, the leakage current 8 flowing through the power linecan be reduced to eliminate adverse effect to other equipment which cancause malfunction. Also, electromagnetic wave generated by the leakagecurrent 8 and the wiring voltage of the leakage current path can bereduced. Therefore, the leakage current 8 can be damped without newlyusing the line filter 5 with built-in common mode transformer 9 toachieve lowering of noise, down-sizing and lowering of cost of theelectric power converter.

[0081]FIG. 18 shows one example of the electric power converteremploying the sixth embodiment of the LC composite element according tothe present invention. The shown embodiment is differentiated from theembodiment shown in FIGS. 1 and 2 in the following points. Eachelectrode of the LC composite element 15 connected to the direct-currentpower line is wound into compressed planular shape to form the sectionof the wound electrodes in a plane perpendicular to a winding axis intoelliptic shape. Furthermore, the magnetic body to be inserted into thecenter of the electrode is formed into a toroidal shape to form themagnetic circuit. Also, a section of the magnetic body in a planeperpendicular to the winding axis is formed into elliptic or rectangularshape. Thus, an effective sectional area of a magnetic path of the barshaped magnetic body 19 can be significantly increased withoutsignificantly increasing effective magnetic path length of the magneticcircuit formed into toroidal shape to increase excitation inductance ofCMT and to improve damping effect of the leakage current 8 of thezero-phase coil 26, the resistor 13 or the variable resistor 27. Thus,the leakage current 8 flowing through the power line can be reducedsignificantly to eliminate adverse effect to other equipment which cancause malfunction. Also, electromagnetic wave generated by the leakagecurrent 8 and the wiring voltage of the leakage current path can bereduced. Therefore, the leakage current 8 can be damped without newlyusing the line filter 5 with built-in common mode transformer 9 toachieve lowering of noise, down-sizing and lowering of cost of theelectric power converter.

[0082]FIG. 19 shows one embodiment of the electric power converteremploying the seventh embodiment of the LC composite element accordingto the present invention. The shown embodiment is differentiated fromthe former embodiment. On the surfaces of the anode and the cathode 16and 17 of the LC composite element are provided regions having mutuallydifferent surface roughness. The regions are provided in strip like formfor connecting respective two connection electrodes 20 connected toanodes and cathodes, respectively. By this, an electrical resistance ofthe region having lower surface roughness on the surface, is lowered torestrict heating to reduce internal heat generation in the LC compositeelement. On the other hand, in the region 16B having large surfaceroughness in the surface, electric capacity can be increased to increasecapacity of the LC composite element to permit formation of the LCcomposite element with low heat generation and high capacity. Thus,lowering of noise, lowering of loss and enhancing conversion efficiencyof the electric power converter can be achieved.

[0083] Naturally, the present invention is applicable as the electricpower converter 52 for linking a power source system of a photo voltaicpower generation system constructed with solar cell 51 and the electricpower converter as shown in FIG. 14, all vehicles and all inverter unitsmounted on the vehicles taking an internal combustion engine 48 and anelectric motor as the load 6 as prime mover, connecting the powerstorage portion 14 to the inverter portion 3 via the LC compositeelement 15 for supplying direct-current power, transmitting drivingtorque of the internal combustion engine 48 and the electric motor ofthe load 6 through a power transmission 49, as shown in FIG. 15.Furthermore, the foregoing embodiments of the electric power converteris applicable for the inverter unit for driving a compressor or fanmotor to be employed in home-use or business-use air conditioner or forthe inductance driving electric power converter for a motor drivingwashing bath of washing machine, a motor of a suction fan of electriccleaner, for generating magnetic field of electromagnetic range and soforth, to achieve lowering of noise, down-sizing and lowering of cost.

[0084] As set forth above, with the present invention, electric powerconverter which can achieve lowering of noise, down-sizing and loweringof cost, can be provided, by winding the anode and the cathode of thecapacitor on the bar-shaped magnetic body, leading the connectionelectrode from both ends of the anode and the cathode, and using theconnecting magnetic body linking both end of the bar-shaped magneticbody to form the magnetic circuit, and employing the LC compositeelement having the third coil interlinked with the magnetic circuit.

[0085] Although the present invention has been illustrated and describedwith respect to exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omission and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodied within a scope encompassed andequivalent thereof with respect to the feature set out in the appendedclaims.

What is claimed is:
 1. An electric power converter including a capacitordisposed in a power wiring for supplying an electric power to a load,comprising: a foil form first electrode fixed on a first insulationsheet; a foil form second electrode fixed on a second insulation sheet;a bar-shaped first magnetic body, on which said first electrode withsaid first insulation sheet and said second electrode with said secondinsulation sheet are wound in overlapping manner to form an LC compositeelement; connecting electrodes electrically connected to respective ofboth ends of said first and second electrodes; a second magnetic bodyhaving both ends located in contact with or close proximity with bothends of said first magnetic body for interlinking both ends of saidfirst magnetic body; a coil wound around said second magnetic body inthe same winding direction as said first and second electrodes woundaround said first magnetic body; and a resistor for shorting the outputof said coil.
 2. An electric power converter as set forth in claim 1,which further comprises: a both end opened cylindrical casing, in whichsaid LC composite element is disposed; seal plates formed of insulationmaterial, fixed on both ends of said cylindrical casing for closing saidboth end opening, and defining through openings, through which saidconnecting electrode and first magnetic body extend; said secondmagnetic body being arranged on outside of said cylindrical casinglinking both ends of said first magnetic body and being fixed sidesurface of said cylindrical casing and said seal plate by a jig oradhesive.
 3. An electric power converter as set forth in claim 2,wherein a jig for fixing said second magnetic body and fixing said LCcomposite element on a wiring board, is secured on said cylindricalcasing.
 4. An electric power converter as set forth in claim 2, whereina jig for fixing said second magnetic body and fixing said LC compositeelement on a wiring board, is secured on said seal plate.
 5. An electricpower converter including a capacitor disposed in a power wiring forsupplying an electric power to a load, comprising: a foil form firstelectrode fixed on a first insulation sheet; a foil form secondelectrode fixed on a second insulation sheet; a bar-shaped firstmagnetic body, on which said first electrode with said first insulationsheet and said second electrode with said second insulation sheet arewound in overlapping manner with placing said first electrode on upperlayer to form a first LC composite element; a bar-shaped third magneticbody, on which said first electrode with said first insulation sheet andsaid second electrode with said second insulation sheet are wound inoverlapping manner in the same winding direction as said first electrodewith said first insulation sheet and said second electrode with saidsecond insulation sheet of said first LC composite element, with placingsaid second electrode on upper layer to form a second LC compositeelement, said second electrode of said second LC composite element beingelectrically connected to said second electrode of said first LCcomposite element for establishing series connection of said first LCcomposite element and said second LC composite element; fourth and fifthmagnetic bodies having both ends located in contact with or closeproximity with both ends of said first and third magnetic bodies forinterlinking both ends of said first and third magnetic bodies; a coilwound around one of said fourth and fifth magnetic bodies in the samewinding direction as said first and second electrodes wound around saidfirst magnetic body; and a resistor for shorting the output of saidcoil.
 6. An electric power converter as set forth in claim 5, whichfurther comprises: connecting electrodes electrically connected torespective of both ends of said first and second electrodes of saidfirst and second LC composite elements; both end opened cylindricalcasings, in which said first and second LC composite elements aredisposed; seal plates formed of insulation material, fixed on both endsof said cylindrical casings for closing said both end opening, anddefining through openings, through which said connecting electrodes andfirst and third magnetic bodies extend; said second magnetic body beingarranged on outside of said cylindrical casing linking both ends of saidfirst magnetic body and being fixed side surface of said cylindricalcasing and said seal plate by a jig or adhesive.
 7. An electric powerconverter as set forth in claim 6, wherein a jig for fixing said fourthand fifth magnetic bodies and fixing said LC composite element on awiring board, is secured on said cylindrical casing.
 8. An electricpower converter as set forth in claim 9, wherein a jig for fixing saidfourth and fifth magnetic bodies and fixing said LC composite element ona wiring board, is secured on said seal plate.
 9. An electric powerconverter as set forth in any one of claim 1, wherein the output of saidcoil is shorted by a variable resistor, and comprises means for varyingresistance value of said variable resistor for a plurality of times, andmeasuring voltage at both ends of said variable resistor at everyoccasion of varying the resistance value, and calculating means forderiving the resistance value of said variable register for minimizing acommon mode current flowing through said LC composite element using thedetected voltage at said variable resistor.
 10. An electric powerconverter as set forth in any one of claim 5, wherein the output of saidcoil is shorted by a variable resistor, and comprises means for varyingresistance value of said variable resistor for a plurality of times, andmeasuring voltage at both ends of said variable resistor at everyoccasion of varying the resistance value, and calculating means forderiving the resistance value of said variable register for minimizing acommon mode current flowing through said LC composite element using thedetected voltage at said variable resistor.
 11. An electric powerconverter as set forth in claim 1, wherein an inverter unit using apulse width modulation system for converting a direct-current power intoan alternating-current power is secured on a side surface of an electricmotor as said load, for integrating said inverter unit with said load,said LC composite element is used for smoothing the direct-current powerof an inverter portion.
 12. An electric power converter as set forth inclaim 5, wherein an inverter unit using a pulse width modulation systemfor converting a direct-current power into an alternating-current poweris secured on a side surface of an electric motor as said load, forintegrating said inverter unit with said load, said LC composite elementis used for smoothing the direct-current power of an inverter portion.13. An electric power converter mounted on a vehicle and having aninverter unit for driving a motor as a load using a pulse widthmodulation system for converting a direct-current power into analternating-current power, wherein an LC composite element is used forsmoothing the direct-current power of an inverter portion.
 14. Anelectric power converter having an inverter unit supplying an electricpower to a power source system with converting a direct-current powersupplied from a solar cell or a power storage cell using a pulse widthmodulation system, wherein an LC composite element is used for smoothingthe direct-current power of an inverter portion.
 15. An electric powerconverter as set forth in claim 1, wherein said first electrode withsaid first insulation sheet and said second electrode with said secondinsulation sheet of said LC composite element for smoothing thedirect-current power of the inverter unit are wound to have compressedplanular shape in cross section on a plane perpendicular to a windingaxis, and said bar-shaped first magnetic body is inserted in the centerportion of the electrode wound into the compressed planular shape. 16.An electric power converter as set forth in claim 5, wherein said firstelectrode with said first insulation sheet and said second electrodewith said second insulation sheet of said LC composite element forsmoothing the direct-current power of the inverter unit are wound tohave compressed planular shape in cross section on a plane perpendicularto a winding axis, and said bar-shaped first magnetic body is insertedin the center portion of the electrode wound into the compressedplanular shape.
 17. An electric power converter as set forth in claim 1,wherein regions having mutually different surface roughness are formedon surfaces of respective anode and cathode of said LC compositeelement.
 18. An electric power converter as set forth in claim 5,wherein regions having mutually different surface roughness are formedon surfaces of respective anode and cathode of said LC compositeelement.